中心性両耳側半盲を呈したエタンブトール中毒の1例

Central bitemporal hemianopsia masqueraded in a case of ethambutol toxicity

　中心性両耳側半盲が82歳男子に発症した。視力は0.6と0.2であった。頭蓋内には病変は発見されなかった。初診3か月後に，初診の10か月前からエタンブトールを一日量1g連続服用していたことが判明した。エタンブトール服用中止6か月後に，視野，色覚，視力が回復した。エタンブトールが視交叉部に限局性の病変をおこしたと推定された。診断確定には問診が有力な手掛りとなった。

A 82-year-old male showed a decrease in visual acuity to 0.6 in the right eye and 0.2 in the left with correction. He presented decreased central fusion frequency, abnormal color vision simulating tritanopia and central bitemporal hemianopsia. Space-occupying lesion in the central nervous sys-tem was ruled out by computed tomography and magnetic resonance imaging. Later it was revealed that he had been under treatment with oral etham-butol at the dosis of 1 g daily during the foregoing 11 months.

Spontaneous recovery of visual acuity set in 3 months later. The visual field also recovered another 3 months later.

Ethambutol may affect the optic tract either diffusely or focally. In either instance, the papil-lomacular bundle appears to be more liable to damage resulting, as in this case, in central hemitemporal hemianopsia.